Lamp sealing and exhausting machine with precision focusing apparatus



Dec. 13, 1955 P. TYLER 2,726,917

LAMP SEALING AND EXHAUSTING MACHINE WITH PRECISION FOCUSING APPARATUS Filed March 28, 1952 4 Sheets-Sheet l Fgi.

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Dec. 13, 1955 P. TYLER 2,726,917

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United States Patent LAMP SEALING AND EXHAUSTING MACHINE WITH PRECISION FOCUSING APPARATUS Leslie P. Tyler, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation of New York Application March 28, 1952, Serial No. 279,023

7 Claims. (Cl. 316-29) 7 This invention relates generally to the manufacture of electric devices such as incandescent lamps and to automatic sealing and exhausting machinery used therein. The invention is more particularly concerned with apparatus for accurately positioning the filament with respect to the bulb after the bulb has been sealed to the mount in an incandescent lamp, but before the bulb has been exhausted and tipped ofif;

It will be appreciated that certain types of incandescent lamps for use in reflectors or projectors, must have their filaments accurately positioned with respect to whatever portion of the lamp is utilized for locating it in the reflector, such portion generally being the base. Unless special precautions are taken, the usual mass-produced incandescent lamp is not manufactured with sufficient exactitude to be satisfactory in this respect. One answer to this problem consists in sealing the mount to the bulb within the usual manufacturing tolerances, and thereafter carefully adjusting the position of the bulb with respect to the base in order to pre-focus the filament during the basing operation. This method of pre-focusing is generally carried out in a basing or finishing machine provided with optical apparatus to assist the operator in accurately positioning the filament. U. S. Patent 2,132,369 Geiger et a1. is typical of the machinery used in this process. In general, this process is entirely satisfactory with very small sizes of incandescent lamps such as miniature flash light lamps where the bulb is hardly any larger than the base, but is not feasible in the larger sizes where these conditions do not hold.

The other method of pre-focusing used with the larger sizes of incandescent lamps, consists in accurately positioning the filament with respect to the bulb immediately after the sealing operation while the seal region where the bulb is fused to the flare of the stem is still plastic enough to permit working. Thereafter the bulb is exhausted, the exhaust tube is tipped ofi, and the bulb is based as accurately as possible without further manual adjustment except possibly as regards orientation ofthe filaments with respect to the base pins when required with bayonet type bases.

This latter method of pie-focusing, that is pre-focusing by accurate positioning of the filament with respect to the bulb, has up until the present time generally been carried out in a sealing machine whereof that described in U. S. Patent 2,021,001 Donovan et al., is typical. This machine, which is of the usual indexing turret type, supports the bulb neck-up so that the exhaust tube projecting upwardly from the neck is readily accessible for grasping by an operator in order to work the seal and position the filament. The lamp is then subsequently exhausted and tipped 01f in an exhausting machine in which it is supported neckdown.

Except where the requirement for accurate pre-focusing has prevented it, the manufacturing process which involves the sealing of a bulb neck-up in a sealing machine and the subsequent exhausting neck-down in a separate exhausting machine, has been largely superseded by a combined sealing and exhausting process carried out in a single machine. The prototype of such combined sealing-exhausting machines, generally known as a sealex machine, is described in U. S. Patent 1,662,045 Patterson with subsequent improvements described in U. S. Patent 2,069,086 Donovan et al. In the combined sealing-exhausting machine, the bulbs are supported neck-down in one series of heads wherein they are sealed to the mounts, and are thereafter transferred without interruption, still neckdown,- to another series of heads on the same turret wherein they are exhausted and the exhaust tubes tipped 01f. It will readily be appreciated that the combined sealingexhausting machine has many advantages from the point of view of speed and economy of manufacture; this follows from the fact that the bulb is heated only once and is not allowed to cool until the time when it is completely exhausted and tipped off. Moreover, the repeated manual handling which must take place when scaling is performed in one machine and exhausting in another is avoided. The advantages to be realized from carrying out the prefocusing operation in a combined sealing-exhausting machine will thus be appreciated.

Accordingly the principal object of this invention is to provide apparatus operating in conjunction with a combined sealing-exhausting machine for accurately prefocusing the filament with respect to the bulb in an incandescent lamp.

Another object of the invention is to provide a mechanism for accurately positioning the sealing head of a sealing-exhausting machine at a certain station to allow the use of fixed optical means for accurate pro-focusing of the filament with respect to the bulb supported in the head.

In the illustrated embodiment of the invention, the bulb arrives at the pre-focusing station supported neckdown in a sealing head. At this station, the flames, which have up until now maintained the seal in a plastic condition, are discontinued, the exhaust tube is uncovered by the downward withdrawal of the hollow spindle which formerly supported it, and the sealing head is accurately fixed in position by reason of its engagement by a pilot slide positioning unit. Simultaneously heat shields are swung into place to protect the operators hand from heat radiated by the sealing head, thereby permitting her to grasp the exhaust tube of the bulb and work the seal, generally with a downward stretch, until the filament is accurately positioned as indicated to her by the optical system. The bulb then continues uninterruptedly on its course through the remaining sealing heads and is then transferred to the exhausting heads for evacuation and tipping off.

For further objects and advantages and for a better understanding of the invention, attention is now directed to the following description and accompanying drawings. The features of the invention believed to be novel will be more particularly pointed out in the appended claims.

In the drawings: 7

Fig. 1 is a schematic diagram relating to the operation of a combined sealing-exhausting machine.

Fig. 2 illustrates the transformations in the bulb and mount at various stations of the machine heads, including the pre-focusing station.

Fig. 3 is a vertical elevation through a section of the turret at the pre-focusing station and showing the optical system and the sealing head positioning unit.

Fig. 4 is a front elevation of the sealing head at the pre-focusing station and showing a fragment of the positioning unit immediately above it.

Fig. 5 is a plan view of the apparatus at the pre-focusing station and including the adjacent stations on either side.

Fig. 6 is a plan section showing the belts and pulleys which control the rotation of the sealing head.

The contribution made to lamp manufacturing by the present invention will be most readily appreciated after consideration of a modern sealing-exhausting machine. Such a machine comprises in general a turret supporting a series of sealing heads disposed in a ring and an equal number of exhausting heads usually disposed in a larger ring at a lower level. For instance, referring to Fig. 1, the schematic diagram represents 16 sealing heads on an inner ring which are indexed through successive stations A to P, and an equal number of exhausting heads on an outer ring, likewise indexable through stations a to p. The turret is rotated intermittently in a counter-clockwise direction, the interval of dwell of the heads at each station allowing the desired operation to be performed thereat.

The function of the machine in general is to seal a mount into a bulb and thereafter evacuate the bulb and tip off the exhaust tube. Referring to Fig. 2a there is shown a vitreous bulb 1 supported in a chuck of a sealing head 2,- and a mount 3 supported on a vertically reciprocable hollow spindle 4 which is also part of the sealing head. The mount 3 comprises in general a stem tube 5 flared at its lower end and pressed at its upper end where the lead wires pass through it to support a filament 6.

An exhaust tube 7 is joined to the stem tube near the.

flare, the stern tube being pierced at the juncture to permit evacuation of the bulb subsequent to sealing.

The mount is loaded into a spindle 4 of a sealing head at station A by an operator. At station B, the spindle, rises and lifts the mount into position for sealing to a bulb. The bulb may be loaded either manually or automatically into the chuck of the sealing head at stations C or D. The head thereafter is indexed through stations E to I where flames are played upon the neck of the bulb by burners indicated at 8 in Fig. 212. During this time, the sealing head is rotated or spun on the turret in order to allow the flames to bear evenly on the entire circumference of the bulb. This assures even heating without the occurrence of any strains in the glass. of the stem tube is also heated by radiation and conduction, and by the time the sealing head has reached station I, the neck of the bulb has collapsed inwardly and fused into the rim of the flare. The mount is thus effectively sealed to the bulb. At stations I and K, hard sharp flames are directed by burners 9 on the neck of the bulb just below the seal so that the neck is severed in that region and the excess portion or cullet 10 drops down on the base of spindle 4, as illustrated in Fig. 20. At station L, the seal is evenly heated by softer flames so as to make it uniformly plastic for the pre-focusing operation to be performed at station M. At the same time the spindle 4 is lowered so as to render the exhaust tube accessible for grasping by an operator at the succeeding station.

At station M, the rotation or spinning of the sealing head on the turret is stopped and the head is accurately positioned with respect to an optical system. The optical system and the positioning mechanism will be described in detail shortly. The pre-focusing operator present at this station grasps the exhaust tube 7 of the bulb with her hand, as indicated at 11 in Fig. 2d, and stretchesthe seal slightly by pulling down on the tube. This operation, commonly known as pull down, frees the seal from strain and makes it strong and serviceable. At the same time, the operator observes the position of the filament through the optical system and works the seal so as to bring the filament into the predetermined focal position. Thus the filament is pre-focused on a sealing head in a combined sealing-exhausting machine without any interruption of the regular course of the bulb through the machine. Atstation N the seal is allowed to cool and begins to harden; by the time the head opens in position The flared portion 4 O, the seal has completely lost its plastic condition and is set hard.

At station P, the bulb is transferred from the sealing head to an exhausting head 12, as shown in Fig. 2e, the

exhausting head being then located at station p. The transfer may be done manually, or automatically by a mechanism such as is described in Patent 2,069,086 Donovan et al. The exhaust tube 7 is received and clamped in the exhausting head, and the bulb thereafter progresses through stations a to o of the exhausting heads, being subjected to a preliminary vacuum in stations a and b, and to repeated evacuation and flushing with nitrogen or other suitable gas through stations 0 to m. It will be appreciated that the combined sealing-exhausting machine has the very decided advantage that the bulbs are transferred to the exhausting heads directly from the sealing heads before they have had a chance to cool and reabsorb impurities such as water vapor from the atmosphere. Moreover the need for reheating and the consequent delay are avoided, resulting in a manufacturing procedure which is much more eflicient.

At station n, if desired, the bulb is filled with argon or other inert gas, and at. position 0 the exhaust tube is tipped off and the finished bulb is ejected from the sealing head into a suitable chute. The result is a sealed pre-focused and exhausted bulb, ready for basing on a finishing machine and requiring no further processing as regards achieving the desired position of the filament with respect to the bulb.

The mechanism which accurately positions the sealing heads with reference to the optical system at focusing station M will now be described in detail, reference being made to Figs. 3 to 6. Referring particularly to Fig. 3, a sealing head indicated generally at 2 and an exhausting head indicated generally at 12 are supported near the rim of a rotatable carrier or turret of which a fragment is shown at 22. The turret may be intermittently rotated through any one of the indexing systems well known to the art, for instance through vertical rollers depending from the turret and a horizontal rotating drum cam such as described in Patent 2,021,001 Donovan et al. The sealing head comprises a base 23 which is supported on a hollow shaft 24 journalling at 25 in the turret 22. The bulb holding frame or yoke 26 is supported vertically above the base 23 by a single side rod 27, best seen in Fig. 4. The use of a single side rod facilitates the pre-focusing operation by making the exhaust tube more readily accessible for grasping by an operator. The rod is preferably made of a low expansion alloy to reduce the effect of heat on the position of the yoke. A bulb 1 is reecived in a generally circular recess 28 in the yoke 26, the recess being open towards the front in order to facilitate insertion or removal of the bulb notwithstanding the depending exhaust tube 7. A. cover 29, hinged to the plate at 30, presses down lightly on the bulb and serves to maintain it firmly Within the opening. A roller 31 carried on a pin at the rear of the cover is adapted to engage a suitable cam track when it is desired to lift up the cover to release the bulb.

Throughout stations A to K before the bulb and the flare of the mount are sealed together, the mount is supported on hollow spindle 4 which the exhaust tube 7 of the bulb enters, the bulb being supported by the engagement of the top end of the spindle with the lower surface of the flare. The spindle passes through the hollow shaft 24, and may be raised or lowered by a cam track 34 on which a shoe 35.attached to the lower end of the spindle, rides. The sealing head may be rotated as a unit with respect to the turret in order to spin the bulb. For this purpose, there is provided a pulley 36 fast on the lower end of the shaft 24 supporting the sealing head unit. When. it is desired to rotate the head 4, a flexible belt such as a rubber band 37 shown in Fig. 6, iscaused to engage the pulley.

A portion of the mechanism for rotating or spinning the sealing heads is shown in Fig. 6. The same notation in connection with the stations has been used as in Fig. 1, M denoting the focusing station. The view is a plan section immediately below the level of the turret frame 22, the outer cross-hatched portions 25 being the journal portions of the turret which support the sealing head shafts 24. The vertically reciprocable spindle 4 appears in section immediately within the seailng head shaft 24. The internal bushing 38 within the spindle is an adaptor suited to the particular size of an exhaust tube of the bulb to be handled, and defines an annular air passage within the spindle for blowing cooling air on the mount when desired.

The sealing heads, up to position K which corresponds to the last cut off position, are driven by reason of the engagement of their pulleys 36 by the flexible band 37. The band is driven by a drive pulley 40 and maintained in tension by idler pulleys 41 and 42. Upon being indexed into station L, the belt drive of the sealing head pulley 36 ceases but its rotation is continued temporarily through a friction drive resulting from the engagement of the upwardly turned flange 43 of the pulley by a friction disc 44 driven by a chain sprocket system 45 from the shaft of drive pulley 40.

it will be appreciated that the sealing heads must arrive at the focusing station M with a predetermined orientation so that the accurate positioning mechanism may operate successfully. The orientation begins at station L where the friction drive continues the rotation of the sealing head until it is arrested by the engagement of a pin 47 on the under side of pulley 36 with a spring loaded stop lever 48 which is pivoted on a bracket 49. At the following index of the turret, the pin 47 enters a curved track 50. The track is continued around the turret up to the bulb loading station D and prevents any rotation of the head until a new bulb has been loaded into it.

It will be appreciated that the orientation of the sealing head which is effected by the entry of the locating pin 47 into the guide track 50 is by no means accurate enough for the pre-focusing requirements in regards to the filament. The final accurate positioning of yoke 26 in the horizontal plane is effected through the operation of a pilot slide mechanism, best seen in Fig. 3 and comprising a generally C-shaped pilot slide member 52 having an upper bearing surface at 53 and a similar lower bearing surface at 54 which ride on a vertical guide bar 55. The guide bar 55 is supported by a heavy frame member 56 serving also to enclose a portion of the optical system to be described shortly. Frame member 56 in turn is supported on a rigid standard 57 which is fixed to the bed plate or frame 58 of the machine. The vertical portion 59 of pilot slide member 52 makes a sliding fit in an opening 61 in the frame member 56. Thus the slide member is maintained in rigid alignment with respect to the frame member 56 and its motion is limited to a straight vertical reciprocation.

Slide 52 carries on its lower portion a generally inverted U-shaped holder 62 on whose dependant legs are mounted two pairs of rollers 63 and 64. These rollers have concave rims and engage pins 65 and 66 respectively in the upper surface of yoke 26 which supports the bulb 1. The rollers 64 are supported in holder 62 without any end play, so that when they engage pin 66, the sealing head is positively positioned tangentially with respect to the turret. Rollers 63 on the other hand have some end play, but the accuracy of the positioning of the sealing head is not thereby diminished because they operate only to position the yoke radially with respect to the position already determined by pin 66 with its cooperating rollers.

The vertical reciprocation of the pilot slide is efifected through the linkage comprising connecting rod 68, bell crank 69 pivoted on standard 57 at 71, long vertical rocker arm 72 pivoted on the standard at 73, and cam disc 74.

Cam disc 74 is fast on a shaft 75 driven by the driving means for the turret in a manner to actuate the pilot slide during the dwell interval of each sealing head at the pre-focusing station. The cam disc causes the rocker arm to rock in a plane normal to the drawing (Fig. 3), and this movement is converted by the bell crank 69 into an up and down movement of connecting rod 63, which in turn imparts a vertical reciprocation to the pilot slide 52.

The optical apparatus in general comprises a pair of optical systems which are adapted to project, side by side on a ground glass viewing screen, a pair of images of the filament seen approximately at right angles one with respect to the other. Both systems are enclosed within a sturdy housing 76 fastened to frame member 56, and thereby rigidly supported on standard 57. Each system comprises an objective lens 77, a first reflecting prism 78, a pair of reverting prisms 79 and 81 which bend the light rays up and then back at a higher level (best seen in Fig. 3), reflecting mirrors 82, and a ground glass viewing screen 83. By reason of the double reflections, the two images of the filament which appear side by side on the viewing screen 83 are erect and real. In other words the top of the filament appears at the top of the image, and likewise the right hand side of the filament appears on the right hand side of the image.

In an actual construction of an optical system as de-. scribed, a magnification of 8 times was obtained and this is in general entirely sufficient for the purpose. It is more convenient to project a shadow image of the filament with a luminous edge or outline rather than a bright image; this is achieved by mounting a pair of light sources behind the bulb, each in line with the objective lens of one of the optical systems. Lamps for this purpose are shown at 85 and 86 and are wired to an electrical terminal box shown at 87. In viewing the screen, the operator is protected from extraneous light by a shield 88 which is fastened to the front of the optical box 76.

The inclined table or platform 89 fastened to bracket 57 is provided to enable the operator to rest her elbow thereon during the pull-down operation. It will be appreciated that for grasping the exhaust tube of the bulb as indicated in Fig. 2d, the operator wears protective gloves, for instance asbestos gloves. In addition, there is provided a heat shield 91 in the form of a stack of thin laminations slotted near their center so as to clear the exhaust tube when positioned under the bulb. The heat shield is supported on the lower end of an arm 92 which is pivoted to the frame at 93 and spring loaded at 94, and which engages at its upper end a cam bracket 95 fastened to the slide member 52. When the pilot slide 52 is reciprocated down to position the sealing head, the roller on the upper end of rod 92 rides on the inclined surface of cam bracket 95, causingheat shield 91 to swing forward under the bulb to protect the operators hand from the heat radiated down from the bulb and its supporting yoke.

It has been found desirable to provide certain protective devices to interrupt the operation of the machine if the sealing head should arrive at the pre-focusing station in a defective condition. Thus if the hinged cover 29 which holds the bulb down in the support yoke should happen to be pivoted up, roller 31 would fail to force back cam track 97 supported on lever 98 which is springloaded at 99, and a control switch 101 actuated thereby will stop the machine. Similarly, should a sealing head carry an over-size bulb or should the bulb be improperly seated in the holder, the hinged cover 29 will ride too high and the sealing head might be damaged at the focusing station. Accordingly there is provided on the slide member 52 a feeler device comprising a lateral bracket 102 which supports a vertically suspended rod 103. When the pilot slide is reciprocated down, the spherical lower end 104 of the rod comes to rest on the hinged cover of the sealing head at the preceding station, that is, at station L. Should the cover be riding too high, the rod 7 will be raised and a switch 195 will be actuated, which, like switch 101, will stop the machine. 7

The invention thus combines into a single machine unit all the apparatus requisite for performing the manufacturing operations of sealing, pre-focusing and finally exhausting. Since the prior art machinery which permitted the sealing and exhausting in a single machine always required that the bulb be held in a sealing head with its exhaust tube down, and this manner of; holding the bulb was believed not suited to the manual operationof pullingdown the seal and pre-focusing the filament, prefocused lamps have not heretofore been made in a combined sealing-exhausting machine. Instead, pre-focu-sed lamps were made in a separate sealing machine which supported the bulbs with the exhaust tube up, in the fashion then believed most suited for grasping by an operator. The present invention therefore, in order to realize its concept of sealing, pre-focusing, and exhausting in a single machine, had firstly to provide a sealing head capable of holding the bulb with the exhaust tube down, and of holding it in such a way that the exhaust tube could conveniently'be grasped byan operator. This first problem was solved by recourse to a sealing head comprising a bulb holding plate or yoke supported on a single off-center rod so as to leave the axis clear for manipulation of the exhaust tube. Thereafter the problem was encountered that such a sealing head by reason of the mode of support of the bulb holding yoke and also by reason of unavoidable play in the machine parts, could not be located with sufiicient accuracy solely through the normal indexing mechanism of the turret. This problem was solved by providing a precision positioning mechanism in the form of a vertically reciprocable pilot slide saving portions adapted to engage cooperating portions of the sealing head at the pre-focusing station. By such means, the top plate of the sealing head is accurately positioned, thereby making it possible to utilize a stationary optical system to assist the operator in adjusting the filament to a predetermined position with respect to the bulb enclosing it.

While a certain specific embodiment has been shown and described, it will be appreciated that it, is intended to be illustrative and not limitative of the invention, and that the various parts may be altered to accommodate bulbs and mounts of various sizes and shapes. The scope of the invention is accordingly to be determined by the appended claims.

I claim:

1. A sealing and exhausting machine for electric lamps, comprising a turret, rotatable sealing heads including means for holding a bulb with a dependent exhaust tube neck down supported on said turret, means for intermittently rotating the turret to index the heads to suecessive stations, optical means fixed at a pre-focusing station for determining the position of the filament in a bulb held in a sealing head, heating means located at a station preceding the pro-focusing station to heat the seal region or" said bulb to a plastic condition, and means cooperating with the sealing heads to position them accurately at the pro-focusing station with respect to said optical means and including movable portions on the machine cngaging fixed portions on the heads during the dwell interval of the heads at said pre-focusing station.

2. A sealing and exhausting machine for electric lamps, comprising a turret, rotatable sealing heads including means for holding a bulb with a dependent exhaust tube neck down supported on said turret, means for intermittently rotating the turret to index the heads to successive stations, optical means fixed at a pro-focusing station for determining the position of the filament in a bulb held in a sealing head, and means for accurately positioning the sealing heads at the pre-focusing station comprising a vertically reciprocable pilot slide having portions adapted to engage cooperating portions of the sealing heads and 8 means lowering the pilot slide into engagement with a sealing head during its period of dwell atthat station.

3. A sealing and exhausting machine for electric lamps oi the typeincluding a vitreous bulb enclosing a filament supported therein on a mount sealed to the bulb and having an exhaust tube projecting therefrom, comprising a turret supported on a vertical axis, rotatable sealing heads each including a base member journalled in said turret and a yoke supported from said base member and above it for holding a bulb neck down with its exhaust tube depending therefrom, means for intermittently rotating the turret to index the heads to successive stations, optical means fixed at a prefocusing station for determining the position of the filament in a bulb head in a sealing head, heating means located at a station preceding the prefocusing station to heat the seal region of said bulb to a plastic condition, and means cooperating with the yokes on the-sealing heads to position them accurately in a horizontal plane at the pro-focusingstation and including movable portions on the machine engaging fixed portions on the yokes of said heads during the dwell interval of the heads at said pre-focusing station.

4. A sealingand exhausting machine for electric lamps of the type including avitreous bulb enclosing a filament supported therein on a mount sealed to the bulb and having an exhaust tube projecting therefrom, comprising a turret supported on a vertical axis, rotatable sealing heads each including a base member journalled in said turret and a yoke supported from said base member and above it for holding a bulb neck down with its exhaust tube depending therefrom, means for intermittently rotating the turret to index the heads to successive stations, optical means fixed at a pro-focusing station for determining the posit-ion of the filament in a bulb held in a sealing head, and means for accurately positioning the sealing head yokes at the pro-focusing station comprising a vertically reciprocable pilot slide having portions adapted to engage cooperating portions of the yokes, and means lowering said pilot slide into engagement with the yoke during the dwell period of the head at that station.

5. A sealing and exhausting machine for electric lamps of the type including a vitreous bulb enclosing a filament supported therein on a mount sealed to the bulb and having an exhaust tube projecting therefrom, comprising a turret supported on a vertical axis, rotatable sealing heads each including a base member journalled in said turret, a yoke for holding a bulb neck down with its exhaust tube depending therefrom and a single off-center side rod supporting said yoke vertically above said base member, means for intermittently rotating the turret to index the heads to successive stations, optical means fixed at a pre-focusing station for determining the position of the filament in a bulb held in a sealing head, a vertically reciprocable pilot slide at the pro-focusing station and having portions adapted to engage cooperating portions of the yokes, and means lowering said pilot slide into engagement with the yoke during the dwell period of the head at that station.

6. A sealing and exhausting machine for electric lamps of the type including a vitreous bulb enclosing a filament supported therein on a mount sealed to the bulb and having an exhaust tube projecting therefrom, comprising a turret supported on a vertical axis, rotatable sealing heads each including a base member journalled in said turret, a yoke for holding a bulb neck down with its exhaust tube depending therefrom and a single off-center side rod supporting said yoke vertically above said base member, means for intermittently rotating the turret to index the heads to successive stations, optical means fixed at a pre-focusing station for determining the position of the filament in a bulb held in a sealing head, a pair of spaced vertical pins on each sealing head yoke, a vertically reciprocable pilot slide at the pre-focusing station, rollers on said slide adapted to engage the pins on said yokes, and means lowering said slide during the dwell period of a head at that station to cause the rollers to engage the pins and thereby position the yoke.

7. A sealing and exhausting machine for electric lamps of the type including a vitreous bulb enclosing a filament supported therein on a mount sealed to the bulb and having an exhaust tube projecting therefrom, comprising a turret supported on a vertical axis, rotatable sealing heads each including a base member journalled in said turret, a yoke for holding a bulb neck down with its exhaust tube depending therefrom and a single off-center side rod supporting said yoke vertically above said base member, a vertically reciprocable mount supporting spindle passing through said base member, means for intermittently rotating the turret to index the heads to successive stations, optical means fixed at a pre-focusing station for determining the position of the filament in a bulb held in a sealing head, a pair of spaced vertical pins on each sealing head yoke, a vertically reciprocable pilot slide at the pre-focusing station, rollers on said slide adapted to engage the pins on said yokes, and means lowen'ng said slide during the dwell period of a head at that station to cause the rollers to engage the pins and thereby posi tion the yoke.

References Cited in the file of this patent UNITED STATES PATENTS 1,329,639 Snavely Feb. 3, 1920 1,724,831 Fagan et al Aug. 13, 1929 1,760,693 Gustin May 27, 1930 1,788,957 Phelps Jan. 13, 1931 2,203,917 Malloy June 11, 1940 

